easystats / easystats/effectsize

Cohen's small/medium/large categories for Epsilon-squared?

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Description

Discussed in https://github.com/easystats/effectsize/discussions/679

Originally posted by jarbet August 15, 2025
I often use epsilon-squared ($\epsilon^2$) effect size when doing the Kruskal-Wallis Test. However, I have a question about interpreting the relative size of $\epsilon^2$. The help page of interpret_epsilon_squared says that Cohen's categories are:

image

However, taking a look at the Cohen 1992 paper, I'm not sure how the above was derived?

image

Should the cutoffs instead be from line 8 of the above Table, which are 0.02, 0.15, 0.35?

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Research direction

Start with discussion 679 and the interpret_omega_squared help page linked in the issue. Compare the documented Cohen categories with the cited Cohen 1992 table, then update the relevant interpretation documentation so the epsilon-squared cutoffs and their source are clear.

Written by the indexing model from the issue text.

Assessment

Tech stack
r
Domain
documentation
Issue type
Documentation
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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